1. Field of the Invention
Colorants or dyes suitable for coloring water immiscible organic liquids, particularly petroleum-derived products, are in general and widespread commercial use. There exists a particular need for coloring or marking petroleum-derived products and for means to identify positively the specific colorant or marking ingredient present, and to determine the concentration thereof.
This need arises primarily through the governmental regulatory action of foreign countries, including certain Provinces of Canada and many European countries, by which taxes are imposed on motive and heating fuels. The tax regulations of some countries (and of some States in the United States) provide that particular dyes and/or chemical markers must be added to taxable or non-taxable fuels, as the case may be, to provide a means for identification to prove or disprove the payment of taxes. For example, Manitoba Regulation 51/66 under the Motive Fuel Tax Act of Canada, provides the following at Paragraph 5 under the caption "Marked and Coloured Motive Fuel":
"Motive fuel used for any of the purposes mentioned in subsection (7) of Section 3 of the Act shall be given a specific colour and separate identity by means of a purple dye and a chemical marker, as may be determined by the minister." PA1 1. They are easily removed from petroleum products to which they are added by the common adsorbents such as clays, charcoal, carbon black and silica. PA1 2. In the instance of diesel fuels which contain a variety of naturally occurring impurities including dispersed carbon black, unstable red, brown, and yellow color bodies, and fluorescent compounds, many of the current dyes simply disappear and cannot be recognized except at high concentrations. PA1 3. Convenient "on-the spot" qualitative tests for the identification of these dyes either do not exist or are relatively complex and time consuming. PA1 4. Quantitative tests for determining the concentration of these dyes in the various petroleum products to which they are added either do not exist or are relatively protracted and cumbersome operations. PA1 5. Some dyes, such as Solvent Red #23 and Solvent Red #24 impart yellowish tints making them rather ineffective for coloring yellowish to brown-colored diesel oil. It would therefore be desirable to provide novel colorants for water immiscible organic liquids, particularly petroleum products, which colorants are highly resistant to removal by the common adsorbents and which colorants may be detected qualitatively by on-the-spot testing and which may be determined quantitatively by convenient laboratory methods. PA1 R.sub.2 is H or alkyl having from 1 to 4 carbon atoms, PA1 R.sub.3 and R.sub.4 are each H, OCH.sub.3, OC.sub.2 H.sub.5 or CH.sub.3, and PA1 R.sub.5, r.sub.6 and R.sub.7 are each H or alkyl having from 1 to 12 carbon atoms, at least one of said R.sub.5, R.sub.6 and R.sub.7 being alkyl. PA1 A convenient sample of the colored fuel (50 to 100 ml.) is shaken vigorously with 1 or 2 grams of an adsorbent such as a clay, or preferably a hydrated silica commercially available under the trademark HI-SIL #233. The mixture is allowed to settle to form a clear upper layer and a sediment, whereupon the color of the clear fuel becomes visible while the conventional added dyes or color bodies naturally present in the fuel are removed by the adsorbent. The characteristic color of the disazo colorant is evident in the clear layer.
It is, of course, necessary that the added dye and/or chemical marker be capable of quick and relatively simple identification by non-scientific personnel. In other instances, and aside from tax matters, there are occasions when it is desirable to mark a particular production batch of fuel or solvent to prove the origin of the material. These instances arise in questions of theft and pollution control. As is readily apparent, any colorant or marker so used must be added in small concentration, should not affect the physical or chemical properties of the substances to which it is added, and should be easily identified by relatively quick and simple means.
The tax laws of some countries, for example, certain Provinces in Canada, prescribe that diesel fuel to be sold for use in powering vehicles on the highway be colorless and bear a higher tax than heating oils which are required to be colored. This higher tax is an important factor in causing the price of diesel fuel to be considerably higher than that of heating oil. However, diesel fuels and heating oils of certain grades have very similar chemical compositions and are virtually indistinguishable in their physical properties. In fact, in many instances their identification as distinct entities defies ordinary chemical analysis.
The theory of providing particular classes of colored heating oils as opposed to non-colored diesel fuels is that visual inspection will serve to identify the non-taxed heating oil by its color and the highly taxed diesel fuel by its lack of color. Thus, a dealer in these commodities may have one tank containing colorless, high priced (and taxed) diesel fuel and another tank containing non-taxed, low-priced and colored heating oil. Unfortunately, this presents opportunities for unscrupulous individuals to evade lawful taxation. One way is to decolorize the low-priced, colored heating oil and then sell the colorless product as the higher priced diesel fuel. Some of the commercially available adsorbents which serve this purpose are carbon black, charcoal, and various clays, silicas and aluminas.
In those countries where the tax laws provide that a highly taxed motive fuel be dyed a specific color, as for example in Great Britain, another form of deception is to dilute the taxed, colored fuel with a colorless, non-taxed fuel of virtually the same composition.
Obviously, what is needed is a colorant or series of colorants which are not removed from petroleum products by the common adsorbents and which colorants may be easily identified and quantitatively determined to thwart the tax dodgers and prevent large-scale tax evasions.